Bottle closures for consumable liquids, for example, olive oil, syrup, spirits and wine, have historically been metal and/or cork material. Cork is made from bark of certain trees, for example, the Cork Oak. Cork has qualities particularly suited to storing liquids in bottles because it features impermeability and a certain level of compressibility that allows for both a tight closure and removability. In contrast to bark, wood fibers do not have sufficient compressibility.
Due to extensive use, however, cork supplies are limited, thereby driving up price. Moreover, cork closures carry with them the risk of a taint that can be passed into the liquid. For example, it has been estimated that as many as seven percent of wine bottles have some level of “corking”, or taint imparted by the cork.
By far, the most popular closure for mass-produced bottled liquids is the metal “screw top cap”. Metal screw tops are formed of a metal skirt and plastic sealing layer. Screw tops extend over the outside of the bottle, as opposed to corks that are inserted into the bottle neck. While screw top caps are not susceptible to taint, screw top caps lack aesthetic appeal, which is particularly disadvantageous for higher-valued products such as fine spirits, fine wine, and higher end olive oil and maple syrup.
In other cases, it has been found that certain polymers can be used for bottle closures that behave in a manner more similar to cork. Polymer closures can have similar compressibility. However, polymer closures similarly suffer from a lack of aesthetics associated with fine spirits, wine and other products. Furthermore, polymer closures are given to “creep”, which deforms the closure over time and can lead to failure.
Some attempts have been made to combine certain materials with the polymer closure to take advantage of the mechanical properties of the polymer while improving the aesthetics. In one example, a closure includes a wooden head or cork head portion glued to a thermoplastic polymer portion. The thermoplastic polymer portion inserts into the bottle, while the wooden head remains outside the bottle and provides a gripping portion for extraction. The drawback of this design is that the glue joints often fail, causing separation of the polymer sealing material from the wood.
What is needed is a bottle closure that has sealing qualities comparable to cork, while having a suitable aesthetic human interface.